The present invention relates to a communication apparatus, a reader/writer, a communication system, and a communication method.
In recent years, a non-contact IC (Integrated Circuit) card that can non-contact communicate with a reader/writer is being widespread used. The reader/writer and the non-contact IC card perform communication by using a magnetic field of a specific frequency such as 13.56 MHz as a carrier wave. Specifically, the communication is carried out by having the reader/writer transmit an encrypted carrier wave signal on the carrier wave, and the non-contact IC card receive the carrier wave and return a response signal (response) (see e.g., Japanese Patent Application Laid-Open No. 2007-279966).
If the communication state is unstable for reasons such as the distance between the reader/writer and the non-contact IC card is far, the reader/writer may not properly receive the response with respect to a communication command transmitted to the non-contact IC card within a predetermined retransmission interval. In this case, the reader/writer guarantees the communication quality by retransmitting to the non-contact IC card a communication command of the same content as the content transmitted to the non-contact IC card immediately before. A parameter indicating the retransmission interval is set for every communication command in the non-contact IC card, where only one set is set in one non-contact IC card.
Such non-contact IC card excels in convenience as it can non-contact communicate with the reader/writer by simply being placed over the reader/writer even if it is placed in a wallet, an IC card holder, and the like. The non-contact IC card is thus applied to various services such as electronic money service, transportation service, and personal authentication service, and the widespread use of the non-contact IC card is increasingly advancing. A function corresponding to a plurality of services tends to be mounted in one non-contact IC card to be load in the portable telephone in the near future.
However, the plurality of services mounted in one non-contact IC card sometimes includes the service requiring higher security level and the service requiring shorter processing time. Thus, the non-contact IC card that can correspond to a plurality of encryption methods is desired. It can be assumed that the processing time differs depending on the high and low of the security level of the encryption method, but an issue in that an optimum retransmission interval may not be applied for every encryption method arises since the parameter indicating the retransmission interval that can be set to one non-contact IC card is only one set.
Therefore, it is desirable to provide an improved communication apparatus that can apply the retransmission interval corresponding to the encryption method, a reader/writer, a communication system, and a communication method.